* {
  margin: 0;
  padding: 0;
}
body {
  /* 设置窗口的高度为100%的窗口高度 */
  height: 100vh;
  /* 伸缩盒子模型 */
  display: flex;
  /* 下面两个属性让body里的子类居中 */
  justify-content: center;
  align-items: center;
  background-color: #2c3e50;
  
}

.container {
  display: flex;
  justify-content: center;
  align-items: center;
  flex-direction: column;
  width: 300px;
  height: 450px;
  border-radius: 20px;
  background-color: #34495e;
  box-shadow: 8px 10px 10px rgba(33, 45, 58, 0.6);
  overflow: hidden;
  position: relative;
}
.container h1{
    margin-bottom: 20px;
    transition: 1.5s;
}

.container:hover h1{
  transform: rotateY(360deg);
 
}

.container form {
  width: 300px;
  height: 200px;
  display: flex;
  justify-content: space-around;
  flex-direction: column;
  align-items: center;
  z-index: 1;
}
.container form .tbx {
  width: 200px;
  height: 40px;
  outline: none;
  border: none;
  border-bottom: 1px solid #fff;
  background: none;
  color: #fff;
}
/* 设置placeholder */
.container form .tbx::placeholder {
  color: #fff;
  font-size: 15px;
}
.container form .sub {
  margin-top: 10px;
  width: 200px;
  height: 40px;
  outline: none;
  border: 1px solid #fff;
  border-radius: 20px;
  letter-spacing: 5px;
  color: #fff;
  background: none;
  cursor: pointer;
}

.container form .sub:hover{
  color: #f1c40f;
}

.container h1 {
  z-index: 1;
  color: #ecf0f1;
  letter-spacing: 5px;
  padding-left: 5px;
  font-size: 50px;
  font-weight: 100;
  text-shadow: 5px 5px 5px rgba(33, 45, 58, 0.3);
}
/* 设置鼠标进入的样式 */
.container .in {
  position: absolute;
  top: 0;
  left: 0;
  display: block;
  width: 0;
  height: 0;
  border-radius: 50%;
  background: #3498bd;
  transform: translate(-50%, -50%);
  /* 使用in动画，持续0.5s,缓出的时间函数，停留在最后一帧 */
  animation: in 0.5s ease-out forwards;
}
/* 设置鼠标离开的样式 */
.container .out {
  position: absolute;
  top: 0;
  left: 0;
  display: block;
  width: 1200px;
  height: 1200px;
  border-radius: 50%;
  background: #3498bd;
  transform: translate(-50%, -50%);
  animation: out 0.5s ease-out forwards;
}
/* 设置鼠标进入时，元素的动画 */
@keyframes in {
  /* 初始关键帧 */
  0% {
    width: 0;
    height: 0;
  }
  /* 结尾关键帧 */
  100% {
    width: 1200px;
    height: 1200px;
  }
}
/* 设置鼠标离开时，元素的动画 */
@keyframes out {
  /* 初始关键帧 */
  0% {
    width: 1200px;
    height: 1200px;
  }
  /* 结尾关键帧 */
  100% {
    width: 0;
    height: 0;
  }
}
